Method and apparatus for connecting a flowline to an offshore installation

ABSTRACT

A method and apparatus for connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having a substantially vertical support positioned on the floor of a body of water and a platform carried by the support. The flowline is positioned at the water surface adjacent the installation and terminated a distance beyond the installation approximately equal to the depth of the water. The portion of the flowline adjacent the installation is slidably connected to the support and the flowline is lowered to the floor of the body of water while gradually bending the flowline in such a manner that the portion of the flowline between the support and its terminal end is substantially parallel to the support when the flowline reaches the floor of the body of water. The terminal end of the flowline is subsequently connected to the platform. In this manner, the flowline has a sufficient curvature to prevent buckling thereof.

O United States Patent [151 3,640,080 Neal Feb. 8, 1972 [54] METHOD AND APPARATUS FOR,

CONNECTING A FLOWLINE TO AN Primary Examifwr-lacob Shapiro OFFSHORE INSTALLATION Attorney-Louis J. Bovasso and J. H. McCarthy [72] Inventor: William J.Nea1, Manvel, Tex. I [57] ABSTRACT [73] Assignee: ShellOil Company, New Y rk, N-Y- A method and apparatus for connecting a flowline having a major portion adapted to lie along the floor of a body of water [22] Flled' 1970 to an'offshore installation of the type having a substantially [21] Appl. No.: 16,794 vertical support positioned on the floor of a body of water and a platform carried by the support. The flowline is positioned at the water surface adjacent the installation and terminated a [5 2] U.S.Cl ..6l/72.3, 72/380 distance beyond the installation approximately equal to the [51] Int. Cl ..Fl6l1/00,B21d 11/02 [58] Field of Search 61/72 1 72 3' 72/380 166/ depth of the water. The portion of the flowhne ad acent the ml 285/18 I stallation is slidably connected to the support and the flowline v is lowered to the floor of the body of water while gradually bending the flowline in such a manner that the portion of the [561 m cued flowline between the support and its terminal end is substan- UNITED STATES PATENTS tially parallel to the support when the flowline reaches the floor of the body of water. The terminal end of the flowline is 3,531,941 10/1970 Vincent ..61/72.3 Subsequently connected to the l tf In i manner, the 3,376,708 4/1968 l-lindman ..61/72. flowline has a sufficient curvature to prevent buckling thereof. 3,434,296 3/1969 Otteman et a1. .....61/72.3 3,503,218 I 3/ 1970 Broadway et a1. ..61/72.3 l1 Claims,4Drawing Figures l5 I? If I 38 36 1 A 24 a 27 as I W PATENIEI] FEB 8 1972 INVENTOR:

WILLIAM J. NEAL HIS ATTORNEY PATENIED FEB 81972 131640.080

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WILLIAM J. NEAL HlS ATTORNEY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to underwater flowlines and more particularly, to a method and apparatus for connecting an underwater flowline to an offshore platform".

2. Description of the Prior Art The development of offshore oil and gas wells frequently necessitates the use of offshore installations or so-called platforms. These installations are used, for example, for drilling and subsequently for producing a well or wells. Accordingly, it is often desirable to provide one or more flowlines from a platform to a remote point, for example, to shore or to another platform. The flowlines may serve many purposes, the most common being to carry off the output of oil or gas from a well. Since the flow line (also referred to as a pipeline) lays in a sub stantially horizontal position along the floor of the body of water in which the platform is located, a problem arises in establishing fluid communication between the flowline and the surface of the platform which is above the surface of the body of water. It will be thus apparent that either the flowline must be bent from its horizontal position on the ocean floor to a vertical position extending to the upper surface of the platform or a separate vertical extension must be installed and connected to the flowline on the ocean floor. The vertical portion is generally referred to as the flowline riser.

The present practice for installing the riser is to provide a vertical flowline or pipeline segment along the side of the platform which extends to the floor of the body of water and is connected to the underwater flowline by divers. However, this is a generally cumbersome and expensive operation, particular in relatively deep water where the divers effectiveness is severely impaired.

At greater than diver depths, connections cannot be made by divers on the ocean floor. In this case, it is known to first connect the riser" to the flowline and lower the assembly down a leg of the platform while simultaneously laying the flowline from a barge proceeding away from the platform. However, the procedure also has drawbacks in that the lowering and laying operation must be carefully programmed to prevent damage to the pipeline and/orriser. In addition, the method is only applicable where a pipeline is laid away from a platform and cannot be readily and easily employed where a pipeline approaches a platform.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method and apparatus for installing a flowline riser to an offshore platform which eliminates the need for making an underwater connection.

Another object of this invention is to provide a method of installing a riser in which the underwater flowline and the riser may be formed of one continuous pipeline.

A further object of this invention is to bend the underwater flowline to provide an upstanding portion which serves as a riser.

A still further object of this invention is to bend the flowline to form a riser while maintaining the radius of curvature above a predetermined minimum so as to prevent buckling of the pipeline.

These and other objects are preferably carried out by connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having a substantially vertical support positioned on the floor of a body of water and a platform carried by the support. The flowline is positioned at the water surface adjacent the installation and terminated a distance beyond the installation approximately equal to the depth of the water. The portion of the flowline adjacent the installation is slidably connected to the support and the flowline is lowered to the floor of the body of water while gradually bending the flowline in such a manner that the portion of the flowline between the support and its terminal end is substantially parallel to the support when the flowline reaches the floor of the body of water. The terminal end of the flowline is subsequently connected to the platform.

. In this manner, the flowline has a sufflcient curvature to prevent buckling thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical view of an offshore installation showing a flowline connected thereto in accordance with the teachings of my invention; and

FIGS. 2 through 4 are vertical views similar to FIG. 1 showing the sequence of steps for carrying out the teachings of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, FIG. 1 shows an offshore installation 10 having substantially vertical support means in the form of a plurality of legs (only legs 11 and 12 being shown for convenience of illustration) adapted to rest on the floor 13 of a body of water 14, such as an ocean. A generally horizontal platform 15 is carried by the legs extending above the water surface 16. A rail 17 extends generally from platform 15 to the ocean floor l3 and is connected thereto in any suitable manner. Although rail 17 is shown as a separate element in FIG. 1, it may form one ofthe legs of the support means and is thus considered to be part of the support means" for supporting platform 15. Suitable bracing 18 may be provided between the legs 11 and 12 for bracing the installation 10.

A bending shoe 19 is slidably connected to rail 17 in any suitable manner and is adapted to tilt or pivot about its point of connection 20 to rail 17. Shoe 19 includes a bending surface 21 adapted to engage a flowline as will be discussed further hereinbelow. Shoe 19 also includes a plurality of slip clamps 22 and 22a or the like. In this manner, flowline 23 may be coupled to shoe 19 by engagement of clamps 22 and 220 as illustrated in FIG. 1. i V

The terminal end 24 of flowline 23 is preferably coupled to a barge or similar vessel 25. The opposite end of flowline 23 extends to a suitable location, such as an on shore location or an offshore gathering station (not shown). Vessel 25 further includes a barge shoe 26 or the like for engaging flowline 23. Shoe 26 is pivotally attached to vessel 25 at clamp 27. Shoe 19 also includes suitable ballast means (not shown), such as a water ballast, for both loweringshoe 19 through the body of water 14 along rail 17 and gradually tilting orpivoting shoe 19 as will be discussed further hereinbelow.

A tensioning barge or similar vessel 28 is coupled to the installation 10 through an anchor line 29. A plurality of floats 30 and 31, two being shown for convenience of illustration, are connected to anchor line 29 and float of water surface 16. Floats 30 and 31 are in turn coupled to suspension cables 32 and 33, respectively, which are coupled to flowline 23 through conventional automaticrelease clamps 34 and 35 at spaced positions along flowline 23. Suitable takeup winches (not shown) may be included in floats 30 and 31 for raising and lowering flowline 23. In this manner, as indicated by the arrows leading from both vessels 25 and 28, and at cables 32 and 33, the flowline 23 may be supported when tension is released and the assembly (i.e., flowline 23, shoe 19, cables 34, 35, etc.) is lowered down rail 17 to the ocean floor 13. A plurality of flowline clamps 36 are preferably disposed along leg 11 of installation 10 at a plurality of spaced intervals for reasons to be discussed further hereinbelow.

In operation, as illustrated in FIG. 1, the flowline 23 is positioned at the water surface 16 adjacent installation 10. The terminal end 24 of flowline 23 is extended past installation 10 to vessel 25 a distance approximately equal to the depth of the body of water 14 from surface 16 to the ocean floor 13. The portion of flowline 23 adjacent the installation 10 is slidably connected to shoe 19 through slip clamps 22 and 22a. A winch line 37 is coupled at one end to one of the clamps, such as clamp 22, and at the other end to a winch 38 on vessel 25. A suitable flowline tensioning device 39 is disposed on vessel 25 for holding flowline 23. At this point, flowline 23 is supported under tension by means of vessels 25, 28, and cables 32 and 33, as indicated by the arrows. When tension is released and water ballast is added to or transferred within shoe 19, the shoe slides down rail 17 as illustrated in FIG. 2. Line 37 is payed out from winch 38 while cables 32 and 33 are controlled in such a manner that flowline 23 is supported as it is being lowered. Also, as illustrated in FIGS. 2 through 4, bending shoe 19 tilts or pivots about its connecting point 20 until bending surface 21 engages flowline 23 (FIG. 3). At this time, additional floats 39 and 40 may be provided between vessel 25 and installation 10. These floats'are in turn coupled to suitable cables 41 and 42, respectively, similar to cables 32 and 33, connected to clamps 22 and 22a. As in the case of floats 30 and 31, takeup winches may also be provided in floats 39 and 40. Thus, the portion of flowline 23 between shoe l9 and barge 25 may be supported as the flowline 23 is being lowered.

Finally, as illustrated in H6. 4, shoe 19 reaches the ocean floor 13 where it is shown as having tilted or pivoted to a substantially vertical position.,The bending surface 21 of shoe 19 gradually bends flowline 23 so that the portion of flowline 23 between shoe .19 and vessel 25 assumes a position substantially vertical (i.e., generally parallel to the legs 11 and 11a of support 12). The floats 39 and 40, and cables 41 and 42, are released for flowline 23. At this time, the terminal end 24 is released from the tensioning device 39 on vessel 25 and the bending shoe 26 may be used to push the flowline 23 to its point of engagement with leg 11. The terminal end 24 of flowline 23 may then be coupled to the platform 15 by any suitable means (not shown) known in the art after fastening the portion of flowline 23 between shoe l9 and vessel 25 to the clamps 36 along leg 11. Clamps 22, 22a, 34 and 35 may then be released from flowline 23 (not shown).

In this manner, the vertical or riser potion of the flowline 23 extending to the upper surface of the platform 15 may be connected to processing equipment handling the output of a well drilled through one of the legs of the platform (not shown) or may be connected directly to a well or to another pipeline leading to the platform. Although the riser is shown in a vertical position, it should be understood that the riser may be installed at any angle from the horizontal (i.e., generally or substantially vertical to installation without departing from the spirit of the invention. For example, the flowline could be bent to a 45 angle and then joined with another section to provide communication with the upper surface of the platform 15. In addition, the riser need not extend to the surface. It may, for example, extend only a short distance past the upper end of the flowline bending shoe 19. Pipe lengths could subsequently be added to the end of the flowline 23 to form a riser extending to the surface of the platform 15.

The degree of a curvature or bending of the flowline 23 may be predetermined from techniques well known in the pipeline art so as to maintain the radius of curvature of flowline 23 above a predetermined minimum so as to prevent buckling thereof. For example, the techniques disclosed in U.S. Pat. No. 3,466,882 may be used.

I claim as my invention:

1. A method of connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having substantially vertical support means positioned on the floor of a body of water and platform means carried by the support means, said method comprising the steps of:

positioning said flowline at the water surface of said body of water adjacent said offshore installation said flowline extending to and past said installation;

terminating said flowline past said installation a distance approximately to a depth of said water from said water surface to the floor thereof;

slidably connecting the portion of said flowline adjacent said installation to said support means; and

lowering said flowlineto the floor of said body of water while gradually bending said flowline so that the portion of said flowline between said floor of body of water and said terminal end is substantially parallel to said support means when said flowline reaches the floor of said body of water.

2. A method of connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having substantially vertical support means positioned on the floor of a body of water and platform means carried by the support means, said method comprising the steps of:

positioning said flowline at the water surface of said body of water adjacent said offshore installation said flowline extending to and past said installation;

terminating said flowline past said installation a distance approximately equal to the depth of said water from said water surface to the floor thereof; slidably connecting the portion of said flowline adjacent said installation to said support means wherein said support means includes a flowline bending shoe means slidably movable along said installation from the water surface to the floor of said body of water wherein the step of slidably connecting said flowline to said installation includes the step of connecting said flowline to said shoe means; and

lowering said flowline to the floor of said body of water while gradually bending said flowline so that the portion of said flowline between said floor of body of water and said terminal end is substantially parallel to said support means when said flowline reaches the floor of said body of water.

3. The method of claim 2 wherein the step of lowering said flowline to the floor of said body of water includes the step of lowering said flowline while lowering said bending shoe means while bending said flowline about said bending shoe means whereby the portion of said flowline between said bending shoe means and said terminal end gradually moves from a substantially horizontal position at the water surface to a substantially vertical position at the floor of said body of water.

4. The method of claim 1 including the step of connecting the terminal end of said flowline to said platform means.

5. The method of claim 3 including the step of maintaining under tension the end of said flowline opposite said terminal end leading away from said platform while lowering said flowline to the floor of said body of water.

6. The method of claim 5 including the step of supporting under tension the portion of said flowline between said shoe means and said terminal end while lowering said shoe means to the floor of said body of water.

7. Apparatus for connecting a flowline to an offshore installation comprising:

substantially vertical support means positioned on the floor of a body of water; platform means carried by the support means; flowline bending shoe means having a bending surface thereon, said bending shoe means being connected to the support means and movable therealong from a position adjacent the water surface of said body of water to the floor thereof, said flowline bending shoe means including flowline connecting means for slidably connecting a flowline thereto; and rotating means operatively engaging said bending shoe means for rotating said bending shoe means from a position whereby a flowline slidably connected to said shoe means is adapted to be substantially parallel to said water surface at said water surface and substantially perpendicular to the floor of said body of water at said floor when moved along said support means from the water surface to the floor thereof. 8.The apparatus of claim wherein said support means includes rail portion and said bending shoe means is slidably movable therealong.

6 9. The apparatus of claim 7 wherein said bending shoe support under tension a flowline being lowered from the water means is pivotable about a pivot point at substantially the W818! Surface 1 h F1 0! thereofpoint of connection of said shoe means to said support means. 11. The method of claim 2 including the step of connecting The apparatus f claim 7 including fl li Support the terminal end of said flowline to said platform means.

means operatively engaging said installation and adapted to 

1. A method of connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having substantially vertical support means positioned on the floor of a body of water and platform means carried by the support means, said method comprising the steps of: positioning said flowline at the water surface of said body of water adjacent said offshore installation said flowline extending to and past said installation; terminating said flowline past said installation a distance approximately to a depth of said water from said water surface to the floor thereof; slidably connecting the portion of said flowline adjacent said installation to said support means; and lowering said flowline to the floor of said body of water while gradually bending said flowline so that the portion of said flowline between said floor of body of water and said terminal end is substantially parallel to said support means when said flowline reaches the floor of said body of water.
 2. A method of connecting a flowline having a major portion adapted to lie along the floor of a body of water to an offshore installation of the type having substantially vertical support means positioned on the floor of a body of water and platform means carried by the support means, said method comprising the steps of: positioning said flowline at the water surface of said body of water adjacent said offshore installation said flowline extending to and past said installation; terminating said flowline past said installation a distance approximately equal to the depth of said water from said water surface to the floor thereof; slidably connecting the portion of said flowline adjacent said installation to said support means wherein said support means includes a flowline bending shoe means slidably movable along said installation from the water surface to the floor of said body of water wherein the step of slidably connecting said flowline to said installation includes the step of connecting said flowline to said shoe means; and lowering said flowline to the floor of said body of water while gradually bending said flowline so that the portion of said flowline between said floor of body of water and said terminal end is substantially parallel to said support means when said flowline reaches the floor of said body of water.
 3. The method of claim 2 wherein the step of lowering said flowline to the floor of said body of water includes the step of lowering said flowline while lowering said bending shoe means while bending said flowline about said bending shoe means whereby the portion of said flowline between said bending shoe means and said terminal end gradually moves from a substantially hOrizontal position at the water surface to a substantially vertical position at the floor of said body of water.
 4. The method of claim 1 including the step of connecting the terminal end of said flowline to said platform means.
 5. The method of claim 3 including the step of maintaining under tension the end of said flowline opposite said terminal end leading away from said platform while lowering said flowline to the floor of said body of water.
 6. The method of claim 5 including the step of supporting under tension the portion of said flowline between said shoe means and said terminal end while lowering said shoe means to the floor of said body of water.
 7. Apparatus for connecting a flowline to an offshore installation comprising: substantially vertical support means positioned on the floor of a body of water; platform means carried by the support means; flowline bending shoe means having a bending surface thereon, said bending shoe means being connected to the support means and movable therealong from a position adjacent the water surface of said body of water to the floor thereof, said flowline bending shoe means including flowline connecting means for slidably connecting a flowline thereto; and rotating means operatively engaging said bending shoe means for rotating said bending shoe means from a position whereby a flowline slidably connected to said shoe means is adapted to be substantially parallel to said water surface at said water surface and substantially perpendicular to the floor of said body of water at said floor when moved along said support means from the water surface to the floor thereof.
 8. The apparatus of claim 7 wherein said support means includes rail portion and said bending shoe means is slidably movable therealong.
 9. The apparatus of claim 7 wherein said bending shoe means is pivotable about a pivot point at substantially the point of connection of said shoe means to said support means.
 10. The apparatus of claim 7 including flowline support means operatively engaging said installation and adapted to support under tension a flowline being lowered from the water surface to the floor thereof.
 11. The method of claim 2 including the step of connecting the terminal end of said flowline to said platform means. 